The recent case of Network Rail Ltd v Williams highlights the need for landowners to take reasonable steps to ensure that Japanese knotweed does not spread from their land to others' land, or they could be liable for hefty damages.

Japanese knotweed is a highly invasive bamboo-like plant that grows incredibly quickly, and can not only cause serious damage to buildings but also depreciate their value, with estimated excavation and disposal costs for small infestations starting in the thousands.

Landowners' responsibility

Landowners must take reasonable measures to prevent or minimise the spread of Japanese knotweed across the boundary of their property. Reasonable measures are judged on a case-by-case basis, but can include treatment of contaminated soil, herbicide treatment and burial of topsoil.

A landowner cannot escape liability through inactivity and should take active steps to manage their land appropriately to ensure they protect themselves from claims.

When are damages payable?

Where Japanese knotweed has encroached on neighbouring land and a landowner has not taken reasonable steps to prevent the spread of the plant, the landowner may be vulnerable to a common law private nuisance claim for compensation.

Compensation may be granted for loss of enjoyment or amenity, where the plant's presence interferes with quiet enjoyment of the land or where the land's value, marketability and/or insurability is adversely affected. However, compensation will not be awarded where only the market value of the land affected has decreased as result of the presence of Japanese knotweed.

Landowners should be mindful of Japanese knotweed and, crucially, ensure appropriate action is taken to ensure that the plant does not spread to neighbouring properties where present.

  • Madeleine Wakeley is a partner in the commercial property team at award-winning law firm VWV, which has offices in Clarendon Road, Watford